This invention relates to an apparatus for noise reduction in a yarn treating system. In particular, it relates to a noise reduction system for use in conjunction with a yarn treating jet for the continuous fluid treatment of running ends of yarn. The jet has yarn passages, with adjacent access slots to facilitate string-up, as well as fluid conduits in communication with each of the yarn passages for delivery of the treating fluid.
Throughout the present specification and claims, the term "dB(A)" (decibels - A-weighted) connotes a unit of measurement of sound level corrected to the A-weighted scale, as defined in ANSI S1.4-1971, using a reference level of 20 micropascals (2.times.10.sup.-5 Newtons per square meter). The term ".DELTA.dB(A)" refers to the difference between two noise levels where each level is expressed in units of dB(A). The term "yarn" is employed in a general sense to indicate strand material, either textile or otherwise, and including a continuous, often plied, strand composed of fibers, filaments, glass, metal, asbestos, paper, or plastic, or a noncontinuous strand such as staple, and the like. An "end" is one or a contiguous group of such strands of yarn. The treating fluid to be used may be virtually any gas which approaches ideal gas behavior, such as air, steam, nitrogen, oxygen, carbon dioxide, etc.
Jets have become widely used in recent years for the treatment of industrial and textile yarns. Different jets are used for the various end uses with specific designs having been developed according to the yarn treatment to be effected. Fluid jets have been utilized for such diverse yarn treating operations a conveying, twisting, crimping, fluffing, localizing the draw point, or otherwise agitating or treating the yarn by means of treating fluid.
All of these jets utilize a fluid which may issue therefrom at high speeds and pressures creating an extremely high noise level. The problem may be further compounded when the treatment comprises a series of fluid treating jets and/or when a plurality of treatment positions are operated simultaneously. The noise produced by operation of a fluid treating jet which has a yarn passage with an adjacent access slot primarily issues from the yarn passage via its exit end and the adjacent access slot.
With respect to sealing of the adjacent access slot, several devices are known. U.S. Pat. No. 3,296,679 relies upon the slideability of a closure plate and gravity to seal the access slot of a fluid treating jet. U.S. Pat. No. 3,905,075 discloses a noise reduction and heat direction system wherein actuating means trips the pivot of noise damping means to cause a wedge to seal the access slot. While the apparatus of both patents effectively seals the access slot during fluid treatment, it is preferred, when viewing the closure of the access slot as a component of a noise reduction system, that this occur substantially simultaneously with closure of a treating jet exit muffler after string-up and alignment. Positioning of the treatment apparatus may, however, preclude the combining of these two actions with the above disclosed apparatuses and therefore, a viable alternate is desirable. One such alternate would be to provide a fluid treating jet the access slot of which is automatically sealed by fluid operation of the jet. Two devices which accomplish this object are described in U.S. Pat. Nos. 3,363,294 and 3,394,440. Both rely upon fluid actuated movement of either the housing or closure means within the housing for the alignment or misalignment of yarn receiving slots during string-up and operation. It would be less expensive to accomplish simultaneous closure via external means rather than by redesigning the jet.
U.S. Pat. Nos. 3,127,729, 3,167,847, and 3,713,509 relate to various noise suppressors for yarn treating jets. The most common method employed to reduce the high noise levels is to substantially enclose the yarn treating jet or its exit end with a sound absorbing material. The actual sound absorbing materials disclosed by these patents are high porosity low density structures (U.S. Pat. No. 3,713,509); rigid sound absorbing material such as glass fibers (U.S. Pat. No. 3,127,729); and foam rubber, felt, or porous plastics (U.S. Pat. No. 3,167,847). Unfortunately, these materials have been found unsatisfactory for use in yarn treating jets where the treating fluid has temperatures in the range of 250.degree. to 500.degree. C. and pressures ranging from approximately 60 to 125 psig, and where the yarn speed is quite high, for example, 6,000 feet per minute. The high temperature of the treating fluid, which is substantially constant during treatment, will cause a rapid deterioration of these materials. An added problem for consideration is that of accumulated contaminant. Contaminant in a jet of the aforementioned type has two primary sources, the finish applied to the yarn prior to its entry into the yarn treating jet and the yarn itself. Some of the finish is instantaneously burnt off or blown off the yarn by the treating fluid inside the jet. Some of the resultant mist will remain inside the jet and muffler and eventually soak into or saturate the muffler components and yarn passageway. Sound absorbing material which cannot be cleaned must be thrown out and replaced due to this contamination. The other contaminant source is the yarn itself, a small surface portion of which is burnt off or abraded off when treating with high temperature fluid, and which accumulates in a fashion similar to that of the finish contaminant. It is therefore desirable to provide a sound absorbing material which functions to reduce noise as well, if not better, than the prior art materials, while extending its useful life. Such a sound absorbing material must be highly resistant to destruction by high temperatures and accumulated contaminant as well as easily removable for periodic cleansing.
None of the prior art patents teach the apparatus of the present invention for use in a yarn treating system wherein the problems of temperature, string-up access, and accumulated contaminant are solved while substantially reducing the noise level.